Doorbells of a generation or two ago had a transformer, a switch (doorbell), and a sonic transducer (chime, ringer or buzzer). Closing the switch completed the circuit powering the sonic transducer. In the past, doorbells have been upgraded with electronic door chimes. Electronic door chimes can be powered, similar to the mechanical ringers of old, when the switch is closed and the electronic door chime receives power. An advantage of electronic door chimes is that they can generate more and different doorbell sounds and have been cost effective replacements for broken mechanical ringers. More recently, Internet of Things (“IOT”) doorbells are gaining popularity.
IOT devices are internet connected sensors and actuators. An IOT doorbell can trigger a message to a person's smart phone or other internet connected device. Some IOT doorbells now include security cameras allowing a person to remotely monitor the happenings outside their door. As many people have discovered, these IOT doorbells are not always compatible with existing doorbells.
FIGS. 1-6, labeled as prior art, illustrate an electronic door chime that has enjoyed wide market acceptance and bears “UL” markings because it has been assessed as safe by UL, formerly Underwriters Laboratories. Those practiced in consumer electronics and product development know that an electronic door chime lacking UL certifications will not be approved for sale by most U.S. retailers or for installation by licensed contractors or home builders. UL 94 and UL 746 specify testing protocols and the classifications that may be applied to plastic materials.
UL 746 testing can establish “RTI” (Relative Temperature Index”) ratings for materials. RTI is the maximum service temperature for a material where a class of critical properties will not be unacceptably compromised through chemical thermal degradation. This spans over the reasonable life of an electrical product relative to a reference material having a confirmed, acceptable corresponding performance-defined RTI. RTI electrical is electrical RTI and is associated with critical electrical insulating properties. RTI impact is mechanical impact RTI and is associated with critical impact resistance, resilience and flexibility properties. RTI strength is mechanical strength RTI or mechanical without impact and is associated with critical mechanical strength where impact resistance, resilience and flexibility are not essential. Those familiar with product certifications are familiar with RTI electrical, RTI impact, and RTI strength.
There are 12 UL 94 specified flame classifications assigned to materials based on the results of these small-scale flame tests. These classifications, listed in descending order for each of three groupings, distinguish a material's burning characteristics after test specimens have been exposed to a specified test flame under controlled laboratory conditions. The six of the classifications of interest here relate to materials commonly used in manufacturing enclosures, structural parts and insulators found in consumer electronic products (5VA, 5VB, V-0, V-1, V-2, HB). The classifications are listed in order from highest (most flame retardant) to lowest (least flame retardant) with 5VA higher than 5VB, 5VB higher then V-0, etc.
FIG. 1, labeled as prior art, illustrates an exploded view of an electronic door chime 101. The electronic door chime 101 can be installed in a two-gang dual voltage junction box 108. The sizes of junction boxes are often specified by the number of “gangs” which is the number of standard sized wired devices the box can accommodate. As electricians know, junction box sizes have standardized sizes as specified by the National Electric Code (“NEC”). A single gang junction box is approximately 2″×4″ with varying depth. A dual voltage two-gang junction box has two single-gang sections and a solid wall between the two sections to thereby isolate one section from the other.
A back piece 107 has a first compartment 127 and a second compartment 128. When installed in the dual voltage junction box, the compartments are on different sides of the solid wall with the first compartment in one section and the second compartment in the other. A transformer 106 is held in the first compartment 127 by screws 111. A circuit board 105 is held in the second compartment by screws 110. A speaker 104 in the first compartment is electrically attached to the circuit board 105. A faceplate 102 is held to the back piece 107 by screws 112 that pass through spacers 114 and thread into the faceplate 102. The spacers 114 are molded into the back piece 107. The illustrated electronic door chime 101 can be wired to two doorbell buttons 109. Two two-wire busses 113 attach the doorbell buttons 109 to the electronic door chime 101. The electronic door chime 101 can produce one sound when one of the doorbell buttons 109 is pressed and a different sound when the other doorbell button 109 is pressed.
FIG. 2, labeled as prior art, illustrates a transformer 106 and circuit board 105 in an electronic door chime 101. The spacers 114 can be seen extending into the compartments 127, 128.
FIG. 3, labeled as prior art, illustrates the back of an electronic door chime 101. Mains electric power, the 120V AC at 60 Hz electric power available in most homes and businesses in the United States, passes into the electronic door chime 101 at the mains power input 116. The mains power input 116 is labeled N, G, and L to indicate which of the wires are neutral, ground, and live. Two doorbell interfaces 115 can be seen providing wiring points for the two-wires busses 113. The inner recesses of the standoffs are also visible.
FIG. 4, labeled as prior art, illustrates a cut view of the front grill of an electronic door chime 101. The faceplate 102 has a row of grooves 117 that can provide air flow into the electronic door chime 101. Baffles 118 at the inner surface help prevent intrusion.
FIG. 5, labeled as prior art, illustrates doorbell buttons 109 connected to an electronic door chime. A first two-wire bus 120 is connected to the “rear door” doorbell interface 115 and to a doorbell button 109. A second two-wire bus 121 is connected to the “front door” doorbell interface 115. Mains power wires 119 pass into the mains power input 116.
FIG. 6, labeled as prior art, illustrates doorbell buttons 109 and electronic door chimes 101 connected by two two-wire buses 121, 122. One of the doorbell buttons is directly electrically connected to the “rear door” doorbell interface 115 by a two-wire bus 120. The other doorbell button is directly electrically connected to the “front door” doorbell interface 115 by the other two-wire bus 121.
The electronic door chime 101 of FIGS. 1-6 is a commercially successful unit at least in part because it is one of the few such devices that has surpassed safety standards and carries UL safety markings. The current generation of IOT doorbells has proven incompatible with many installed mechanical door chimes and electronic door chimes. Systems and methods for electronic door chimes that are compatible with current generation IOT doorbells and that are certified as safe is needed.